1. Field of the Invention
The present invention relates to a catalyst composition and a process for manufacturing the same. More particularly, the present invention relates to a catalyst composition for hydrotreating of hydrocarbon oils which comprises a micropore alumina or a micropore alumina-containing carrier which comprises an active metal belonging to Group VIB of the Periodic Table and an active metal belonging to Group VIII of the Periodic Table, wherein said active metals are supported by said alumina or alumina-containing carrier at a higher concentration in the center than on the outermost surface of the catalyst particle, and to a process for manufacturing such a catalyst composition. The catalyst composition exhibits a high activity for a prolonged period of time.
2. Description of the Background Art
Topping residue, vacuum gas oil, and vacuum residue obtained by topping distillation or vacuum distillation of crude oils contain large amounts of sulfur compounds and metals. Their contents vary depending on types of crude oils. Burning of these heavy hydrocarbon oils involves generation of toxic substances such as sulfur oxides (SO.sub.x) and the like, which are the causes of furnace corrosion and air pollution. When heavy hydrocarbon oils are catalytically treated to be cracked into lighter fractions, sulfur compounds, nitrogen compounds, and metals act so as to deactivate catalysts. This is a serious cause which prevents effective utilization of heavy hydrocarbon oils. In order to overcome this problem by removing metals and sulfur in the sulfur compounds, heavy hydrocarbon oils containing large amounts of sulfur compounds and metals are treated under hydrogen pressure with a catalyst comprising Group VIB metal, e.g., molybdenum, chromium, tungsten, or Group VIII metal, e.g. iron, cobalt, nickel, platinum, supported on alumina or an alumina-containing carrier.
Such a treatment, however, does not give a satisfactory result. In particular, the catalyst activity seriously deteriorates due to deposition of metals contained in hydrocarbon oils and carbonaceous materials, i.e., decomposition products of hydrocarbon oils, thus significantly lowering the catalyst activity and unduly reducing the desulfurization rate. Development of a catalyst composition for the hydrotreatment of hydrocarbon oils, of which the activity is not inhibited by carbonaceous materials and metals, especially by metals, has therefore been desired.
The present invention therefore provides a novel catalyst composition for hydrotreating of hydrocarbon oils which is poisoned only with difficulty by metals contained in hydrocarbon oils and maintains its desulfurization activity for a prolonged period of time, as well as a process for manufacturing such a catalyst composition.